Large-size klystrons operating in the 300-3000 MHz frequency range with pulsed RF outputs in the 1-2 megawatt power range have been used increasingly in ground-based radar systems and in particle accelerator systems in recent years. In a growing number of applications, such as those requiring Doppler measurements on tumbling radar targets and precisely timed excitations of accelerator cavities, there is a need for more accurate control of the phase and amplitude of the klystron output. For such applications, conventional RF amplitude control loops and RF phase-locked control loops are found to be only marginally adequate because they do not fully compensate for errors in the phase and amplitude of the output pulses.
Some of the prior art systems addressing the problem of phase and amplitude control include a combination of RF feedback and feedforward corrections as discussed in "Control of Cavities with High Beam Loading," Boussard, D., IEEE Transactions on Nuclear Science, Vol. NS-32, No. 5, October 1985; the use of beam loading interaction employing AF feedback loop for amplitude, phase, and cavity loading including use of loops to compensate for cross coupling, described in "Beam Loading Effects in the CERN PS Booster," Pedersen, F., IEEE Transactions on Nuclear Science, Vol. NS-22, No. 3, June 1975; and use in a linear accelerator of a computer model of an amplitude and phase control system for automatic adjustment of the feedforward beam combination pulse and use of a phase step during detuned turn-on, as described in "New Methods of RF-Control for the SNQ," Schulze, D., Kernforschungszentrum Karlsruhe, Institut fur Kernphysik, Postfach 3640, D-7500 Karlsruhe, Federal Republic of Germany, June 25, 1981.
One inherent difficulty is that the conventional RF amplitude and phase control loops do not provide for automatic self-assessment of the initial errors otherwise prevailing at the beginning of each RF output power pulse, and the gradual elimination of these initial errors from the succeeding output pulses. These and other problems of control of megawatt klystrons or other pulsed RF power devices are overcome by this invention.